The invention relates to an electro-optical device having a multilayer coating set. More particularly, the invention relates to a multilayer coating set that provides a moisture and gas barrier for the electro-optical device and enhances resistance of the electro-optical device to chemical attack.
Electro-optical devices, such as electrochromic devices, liquid crystal displays (also referred to hereinafter as “LCDs”), organic light emitting diodes (also referred to hereinafter as “OLEDs”), light emitting diodes (also referred to hereinafter as “LEDs”), photovoltaic devices, radiation detectors, and the like, comprise an electronically or optically active portion—e.g., liquid crystals, a light emitter, or radiation detector—that is frequently disposed on a substrate. In those applications where a rigid electro-optical device is either preferable or acceptable, either glass or silicon is generally used as the substrate. In those applications where a flexible electro-optical device is desired, a polymeric film may serve as the substrate. However, moisture and oxygen diffuse rapidly through such polymeric film substrates, thereby causing the performance of the electro-optical devices disposed on the substrate to degrade or even fail. In addition, polymeric substrates are also subject to attack by chemicals used during processing of the electro-optical device. Finally, many electro-optical applications require a substrate that is thermally stable and transparent in at least the visible light range.
Various single layer coatings have been used to modify the barrier properties of polymeric substrates for use in flexible electro-optical devices. A single layer coating, however, tends to provide a less than optimum barrier against moisture and oxygen. In addition, a single coating cannot meet all of the other requirements, such as mechanical, adhesion, electronically conductive, optical, thermal stability, chemical resistance, and thermal expansion criteria for such electro-optical devices. Multilayer coating composites comprising individually deposited layers have been used to provide the desired moisture and gas barrier properties for such electro-optical devices. However, such multilayer composites do not typically meet all of the other mechanical, adhesion, electric conductivity, optical absorption and/or reflectivity, thermal stability, and thermal expansion requirements for such electro-optical devices. The necessary combination of vacuum and wet processes complicates the manufacture of electro-optical devices that include such multilayer composites.
Therefore, what is needed is a multilayer coating set that provides a moisture and oxygen barrier and resistance to chemical attack during processing while simultaneously meeting the mechanical, adhesion, electronically conductive, optical, thermal stability, and thermal expansion requirements for electro-optical devices, such as LCDs, OLEDs, LEDs, photovoltaic devices, radiation detectors, and the like. What is also needed is a method of depositing such a multilayer coating set on a polymeric substrate using only vacuum-based deposition techniques. Finally, what is needed is an electro-optical device having such a multilayer coating set.